What is PrEP?
PrEP stands for pre-exposure prophylaxis. This involves taking medication to prevent HIV infection prior to potential exposure to HIV, unlike post exposure prophylaxis (PEP) which is taken after possible HIV exposure.
PrEP is a combination of two drugs; tenofovir disoproxil fumarate and emtricitabine, which are 2 antiretrovirals that has been used successfully to control and manage HIV for many years. This has been shown to be highly effective in preventing HIV infection if taken correctly. Major trials were carried out to determine the effectiveness of PrEP ranging from 86% (in PROUD and IPERGAY study) to 90% (PARTNER study).
There are two ways to take PrEP, either daily or ‘on demand’. Daily PrEP is taken one tablet once a day. It needs to be taken same time every day and if PrEP is missed at times of unprotected sex, there is a risk of HIV infection. ‘On demand’ PrEP also known as event based PrEP means taking tablets just before (2 tablets, 2 to 24 hours before the sex) and a little while after planned sexual activity (2 further doses in the 48 hours after sex).
PrEP only protects against HIV and it doesn’t protect against other sexually transmitted infections. Therefore PrEP is not a replacement for condoms and should therefore be used jointly with PrEP.
Who should consider taking PrEP?
PrEP would be of benefit to people who are at higher risk of HIV infection, such as
Men who have sex with men
Trans men and women
People with partners from parts of the world where the rate of HIV infection is much higher
People with an HIV positive partner who does not have an undetectable viral load
There are situations where PrEP may be particularly advised such as
Men who have sex with men who have had a recent sexually transmitted infection (particularly in the rectum/anus)
Those who have used PEP in the past following a sexual risk
People who do chemsex
PrEP and side effects
The majority of people taking PrEP do not report any side effects
Possible side effects of taking PrEP include nausea, diarrhoea, bloating and headaches. These side effects will usually settle after the first month.
PrEP can also affect the kidneys. This is why monitoring is important. In the small proportion of people taking PrEP who developed reduced kidney function, these changes reversed on stopping PrEP.
PrEP can also reduce bone density by 1-5%, causing slight thinning of the bones, however this loss reverses after PrEP is stopped.
Speak to a GU specialist if you are interested in PrEP
Regular monitoring and follow up as recommended by the GU Specialist
Try to take your PrEP pills at a regular time each day
Still use condoms to reduce the risk of catching other STIs
Tell us if your medical history changed or you started new medications including over the counter, herbal or recreational drugs.
Start PrEP without taking an HIV and a kidney test
Start or stop PrEP without seeking specialist advice
Miss taking any pills
Use PrEP as a replacement for condom use
This is part of a series of monthly posts by:
Dr Donia Gamoudi.
Genitourinary (GU) Medicine doctor
MD,MRCP(UK), Dip GUM, DFSRH, Dip HIV